This invention is directed to an organosilicon resinous composition which has been found to have particular utility as a replacement for fluoroelastomers currently being used as lubricants in the extrusion of thermoplastic resins.
When a high molecular weight thermoplastic resin is extruded through a die, it is known that smooth extrudates can only be obtained up to certain shear stresses. Beyond that, surface irregularities begin to appear such as haze and what is known in the art as "sharkskin". These irregularities limit the production rates in commercial applications.
To counteract this undesirable phenomenon, and to enable production at higher rates, lubricants are added to the thermoplastic resin prior to extrusion. One of the primary functions of a lubricant is to delay, suppress, or eliminate, the onset of surface flow defects such as haze and "sharkskin, and to enable operation at higher shear stress.
Fluoroelastomers are currently being used in industry as lubricants for extruding thermoplastic resins. The addition of 250 to 3,000 parts per million of the fluoroelastomer lubricant, delays the onset of melt fracture to higher shear rates and produces smoother extrudates. Typically, these lubricants are added to the thermoplastic resin prior to extrusion by dry blending the lubricant with the resin.
It has been discovered in accordance with the present invention, however, that certain organosilicon compounds, namely organosilicon resinous compositions, are capable of functioning as lubricants for the extrusion of thermoplastic resins, and are as effective, if not more effective, than current commercial fluoroelastomeric lubricants being used in the industry.
These organosilicon resinous compositions provide a viable alternative to the current commercial fluorelastomeric products, and are useful in alleviating what has heretofore been considered difficult extrusion operations.